@torontob:
1- If I am not wrong there is an snmp package on pfsense but I have never worked with snmp. I am exploring Cacti now. So, would cacti try to connect to snmpd or does snmpd connect to cacti and give it the information? (I want to know for security reason so I know which ports need to be opened or not)
SNMP is built-in, Services > SNMP. Just enable it and the modules listed on the screen. Cacti would connect to the pfSense box via snmp and gather the info. A standard unix host template in Cacti should get the right info, if I remember right. You'd just need to allow udp/161 from the box running Cacti to the router.
@torontob:
2- Would using syslog to send logs over the internet and the snmp logs use a lot of my bandwidth or otherwise stress the router if I am planning to log everything?
It wouldn't use a ton of bandwidth in most cases really, but I wouldn't do either of those in the clear across a WAN link. If you must do that to a remote box, setup a VPN for it.